Loss of the Y chromosome is one of the most frequent cytogenetic abnormalities observed in human prostate cancer. However, the biological significance of this event is presently unknown. Sex-region Y (SRY) is a gene which maps to Yp11.3 and has been shown to be the trigger gene for male development in humans and mice. The SRY protein contains a highly conserved AT amino acid region homologous to the HMG box found in many transcriptional activators. Dr. Tricoli and coworkers have demonstrated that this gene is alternatively expressed in prostate cancer with transcripts detected in 60% of the tumors examined. In the 40% of tumors in which SRY transcript is absent, it is not due to any reduction in the SRY gene content of the tumor cells. The goals of Dr. Tricoli's proposal are to understand the significance of Y chromosome loss in prostate cancer as it relates to SRY expression, and to identify factors responsible for regulation of the SRY gene in prostate cancer cells. These studies will be conducted using fresh prostate tumor tissue and the prostate carcinoma cell lines PC-3, DU145, LNCaP and TSU-PR1. These studies will include interphase FISH analysis of touch preparations taken from tumors to determine the frequency and extent of Y chromosomal loss. These studies will be complemented by molecular analysis for regional Y loss using regional mapped Y chromosomal probes and DNA purified from tissues adjacent to touch preparation sections. The result of these studies will be correlated with tumor stage and grade to determine if Y loss is associated with more advanced clinical disease and with patient age and race. Dr. Tricoli and coworkers will examine the effects of factors which could potentially regulate SRY expression in these cells. These include the hormones testosterone, dihydrotestosterone and estradiol and the growth factors of FGF-beta, PDGFa, TGF-beta and EGF. Finally, Dr. Tricoli will determine the effects of SRY gene expression on prostate tumorigenesis by expressing the gene in the SRY deficient cell line PC-3 followed by injection of the cells into C.B17scid mice. The goal of this experiment will be to use the SRY expression PC-3 cells to identify genes expressed downstream of SRY that may be important to the etiology of prostate tumor progression and the normal function of the SRY gene pathway. The data generated from these studies will: 1) define any relationship between Y chromosome loss and advancing tumor stage and grade and patient age, race and disease-free survival, 2) identify mechanisms of SRY gene regulation and 3) determine biological effects of SRY expression on tumorigenic growth, and the identification of novel genes which are expressed downstream of SRY.